This invention relates to Abbe refractometers and more particularly to a follower mechanism for determining the mirror position in an Abbe refractometer.
Abbe refractometers are devices for determining the index of refraction of materials with a high degree of accuracy. The measurement is conventionally made by moving a pivotable mirror until a shadow line created by the sample and primary prism is located precisely at the junction of a pair of cross hairs in an eyepiece. The index of refraction is then obtained by reference to a scale and indicator mechanism coupled to the moveable mirror. The optics of such a system are illustrated in copending application Ser. No. 802,741 filed June 2, 1977. The description and drawings of the application are incorporated herein by reference. Referring to FIG. 8, light from illumination source 101 is directed through primary prism 102 having a test sample (not shown) therein to movable mirror 103. Light reflected from the mirror passes through color-compensating prism 104 and is focused by telescope lens 105 on reticle 106 which is observed through eyepiece 107. Sample temperature is a factor which is capable of exerting a substantial influence on the accuracy of the measurement. Therefore, conventional instruments usually of some means of holding the test prism at a constant temperature, frequently, by means of circulating water from a constant temperature bath. These conventional devices have substantial disadvantage in difficulty of maintaining the constant temperature of the bath and accurately monitoring the temperature of the primary prism. In addition, delays result when starting up circulation of the constant temperature fluid and in bringing the constant temperature fluid to a stabilized temperature.